Mihara (三原市, Mihara-shi) is a city located in Hiroshima Prefecture, Japan.

Most of the current central city area is reclaimed land, and steep mountains approach the coastline, while the northern part is a highland area with an elevation of 400 meters or more at the southern tip of Kibi Plateau, and the western part is mostly hilly.

The Mihara area is part of ancient Aki Province and has been settled since prehistoric times.

Following the Meiji restoration, the town of Mihara was established on April 1, 1889 with the creation of the modern municipalities system.

Mihara has a mayor-council form of government with a directly elected mayor and a unicameral city council of 25 members.

Mihara, collectively with the town of Sera, contributes three members to the Hiroshima Prefectural Assembly.

In terms of national politics, Mihara is part of the Hiroshima 5th district of the lower house of the Diet of Japan.